We have a whole bunch of these sturdy 3-sided corners and 2-sided L-shapes made of tape wrapped around styrofoam sandwiched between wood and cardboard that were used for furniture shipping. They are about 4 1/2 x 4 1/2 x 7 1/2 inches.
We have a whole garbage bag full of them. They are clean and in good shape and would be great for packing/moving furniture.